Saudi Arabia executed two men from Chad on Thursday for their part in a militant attack a decade ago, its Interior Ministry said.

Issa Saleh Hassan Barkaj and Ishaq Issa Ahmed Shakila were executed in Mecca on Thursday morning, the ministry said in a statement on Saudi Press Agency. Death sentences in Saudi Arabia are usually carried out by public beheading.

The pair were convicted of joining an al-Qaida cell; of embracing takfiri ideology, the practice of proclaiming others infidels; of killing French national Laurent Barbot in 2004; and of the attempted shooting of foreign officials.

Saudi Arabia detained over 11,000 people during and after the al-Qaida attacks that targeted Western expatriates and government officials from 2003-06, killing hundreds, and eventually crushed the group inside the kingdom's borders.

Many of those convicted have since been sentenced to death.

Others were given long prison terms for their part in the attacks and for other militant activities, such as travelling overseas to fight or spreading jihadist ideology.

Over the past year, a new wave of attacks, mostly claimed by Saudis sympathizing with Islamic State, have killed dozens in suicide bombings and shootings in the kingdom. So far, they have targeted security officials and members of the Shi'ite Muslim minority.

Al-Qaida, Islamic State and Saudi Arabia's Al Saud ruling family all share a belief in conservative Sunni Islam and the rigid implementation of sharia law.

But both militant groups regard the ruling family as illegitimate, accusing it of
corruption and of betraying Muslims through its close ties to the West.

The Al Saud have mobilised clerics from the kingdom's Wahhabi Sunni school to denounce militants as un-Islamic "deviants" and to pass judgment on suspected jihadists in sharia trials.